The present invention relates broadly to a harrow and more specifically to means for attaching a spring tine to the mounting bar of a harrow.
A primary problem in the design of a harrow attachment or similar implement utilizing a spring tooth tine is that stresses near the point of connection of the tine to the mounting bar result in premature breakage of the tine. The tine must be able to adequately flex when pulled forwardly through the soil. Also, to prevent excess stresses in the tine, it must be able to pivot or swing forwardly about a generally transverse, horizontal axis when the harrow is reversed. The tines often break when the harrow is reversed while the tines are still engaging the ground.
When the tines strike an object and flex rearwardly, they tend to spring forwardly with a considerable amount of force as the object is cleared. This recoiling action can cause excess vibration and stresses in the tine, particularly near the mounting.
Previous means for mounting double-coil spring tines such as described in U.S. Pat. Nos. 3,049,184 and 3,016,958 have not been entirely satisfactory since the tines have a tendency to break near the points of connection to the tooth bars because of the bending loads there. The tine pairs are not freely pivotable in the forward direction as the implement is moved rearwardly. If the tines are in contact with the ground or strike a bank of dirt or other obstacles while the implement is being moved rearwardly, the tines can break. When the tines strike an object and flex rearwardly during a tilling operation, they tend to recoil after the object is passed, providing additional stresses near the connection points as the tines rebound forwardly passed the working position.
Freely pivoting tines which overcome some of the above problems are available on a few harrows which use a circular mounting bar. The double-coils are wrapped around the bars, and a pair of stops located on the bar between each pair of coils contact the portion of the tine joining the coils to hold the tine in the working position as the unit moves forwardly. When the implement is reversed, the tine rotates about the bar allowing the soil contacting teeth to swing forwardly and up from the working position. This type of tine, however, is difficult to mount or replace. The tines have to be mounted in order as the bar is assembled onto the support arms of the implement. If a center tine breaks, all the tines up to and including the broken one have to be slipped off the bar before a new one can be mounted. Often the pair of stops for each tine must be removed also. Therefore, replacement of the tines is very time-consuming.